Method for controlling transmission power of wireless device

ABSTRACT

A method for controlling transmission power of a wireless device is provided. A WiFi link is established to a communication device. A data rate of data packets transmitted to the communication device is monitored. Information from the communication device is obtained in response to the transmitted data packets. A transmission power of the wireless device is decreased when the data rate of the data packets reaches a highest data rate and the first information satisfies a specific condition.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a Divisional of copending application Ser. No.13/348,941, filed on Jan. 12, 2012, which claims priority under 35U.S.C. §119(e) to U.S. Provisional Application No. 61/521,151, filed onAug. 8, 2011, all of which are hereby expressly incorporated byreference into the present application.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a wireless device, and more particularly to amethod for controlling transmission power of a wireless device.

Description of the Related Art

In recent years, mobile phones have become more popular and have variouspowerful applications, such as “Hot Spot” wireless fidelity (WiFi)wireless Internet connection, which provides Internet access over awireless local area network (WLAN) for users nearby a mobile phone.However, the mobile phone functioning as a Hot Spot will consume lots ofpower due to the mobile phone operating in a transmission mode.

Therefore, it is desired to save power for mobile devices in atransmission mode.

BRIEF SUMMARY OF THE INVENTION

Methods for controlling transmission power of a wireless device and awireless device are provided. An embodiment of a method for controllingtransmission power of a wireless device is provided. The methodcomprises: establishing a WiFi link to a communication device;monitoring a data rate of data packets transmitted to the communicationdevice; obtaining first information from the communication device inresponse to the transmitted data packets; decreasing a transmissionpower of the wireless device when the data rate of the data packetsreaches a highest data rate and the first information satisfies aspecific condition.

Furthermore, an embodiment of a method for controlling transmissionpower of a wireless device is provided. The method comprises:establishing a WiFi link to a communication device; transmitting datapackets to the communication device according to a first transmissionpower; adjusting a data rate of the data packets according to a packeterror rate (PER); transmitting data packets to the communication deviceaccording to a second transmission power smaller than the firsttransmission power when the data rate of the data packets reaches ahighest data rate and the PER satisfies a specific condition; andtransmitting data packets to the communication device according to thefirst transmission power when the data rate of the data packets reachesthe highest data rate and the PER does not satisfy the specificcondition.

Moreover, a wireless device is provided. The wireless device comprises aprocessor, an antenna and a radio frequency (RF) module coupled betweenthe antenna and the processor. The RF module comprises a power amplifierwhich transmits data packets from the processor to a communicationdevice with a first transmission power. The processor establishes a WiFilink to the communication device via the RF module and the antenna, andobtains first information from the communication device in response tothe transmitted data packets. The processor controls the power amplifierto transmit the data packets with a second transmission power smallerthan the first transmission power when a data rate of the data packetsreaches a highest data rate and the first information satisfies aspecific condition.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 shows a schematic diagram illustrating IEEE 802.11 wirelessfidelity (WiFi) network communications between two electrical devices;

FIG. 2 shows a block diagram illustrating a WLAN module equipped in awireless device according to an embodiment of the invention;

FIG. 3 shows a method for controlling transmission power of a wirelessdevice with the WLAN module of FIG. 2 according to an embodiment of theinvention;

FIG. 4 shows a method for controlling transmission power of a wirelessdevice with the WLAN module of FIG. 2 according to another embodiment ofthe invention;

FIG. 5 shows an exemplary diagram illustrating the relationships betweena data rate and input power (RSSI).

FIG. 6 shows a method for controlling transmission power of a wirelessdevice with the WLAN module of FIG. 2 according to another embodiment ofthe invention;

FIGS. 7A and 7B show a method for controlling transmission power of awireless device with the WLAN module of FIG. 2 according to anotherembodiment of the invention;

FIG. 8 shows a schematic diagram illustrating a mobile networkcommunication system according to an embodiment of the invention; and

FIG. 9 shows a schematic diagram illustrating an internet networkcommunication system according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

FIG. 1 shows a schematic diagram illustrating IEEE 802.11 wirelessfidelity (WiFi) network communications between two electrical devices 10and 20, wherein the electrical devices 10 and 20 may be computers,portable devices (such as mobile phone, tablet computer) and so on. InFIG. 1, the devices 10 and 20 are equipped with wireless local areanetwork (WLAN) modules (e.g. 802.11b, 802.11g or 802.11n) to performpeer to peer communications. When one of the electrical devices 10 and20 uses a highest data rate to transmit data packets to the otherelectrical device, e.g. 11 Mbps for the 802.11b specification, 54 Mbpsfor the 802.11g specification or MCS7 for the 802.11n specification, theone of the electrical devices 10 and 20 will perform a method to controltransmission power of the WLAN module thereof according to an embodimentof the invention, so as to achieve lower power consumption.

FIG. 2 shows a block diagram illustrating a WLAN module 100 equipped ina wireless device (e.g. 10 or 20 of FIG. 1) according to an embodimentof the invention. The WLAN module 100 comprises a Baseband chip 110 anda radio frequency (RF) module 120. The RF module 120 is coupled betweenthe Baseband chip 110 and an antenna 170, which comprises a low noiseamplifier (LNA) 130, a power amplifier (PA) 140 and a TX/RX processingunit 150. The TX/RX processing unit 150 receives and modulates the dataDAT_(out) from a processor 160 of the Baseband chip 110, so as toprovide the RF signal RF_(out) to the antenna 170 via the PA 140 fortransmitting data packets to another wireless device. Simultaneously,the processor 160 of the Baseband chip 110 further provides a controlsignal Ctrl to the PA 140 for controlling transmission power of thewireless device. In general, the receiving wireless device will sendback acknowledge (ACK) messages in response to the data packetstransmitted by the transmitting wireless device. Therefore, the TX/RXprocessing unit 150 of the transmitting wireless device will receive anddemodulate the RF signal RF_(in) corresponding to the ACK message viathe LNA 130 and the antenna 170, so as to provide the data DAT_(in) tothe processor 160 of the Baseband chip 110, and then the processor 160of the Baseband chip 110 obtains a packet error rate (PER) according tothe data DAT_(in). The PER is the number of incorrectly received datapackets divided by the total number of received packets, wherein apacket is declared incorrect if at least one bit is erroneous.Therefore, the smaller the PER, the better the communication quality.When the receiving wireless device and the transmitting wireless deviceapproach each other, the processor 160 of the Baseband chip 110 willobtain a better PER.

FIG. 3 shows a method for controlling transmission power of a wirelessdevice with the WLAN module 100 of FIG. 2 according to an embodiment ofthe invention. Referring to FIG. 2 and FIG. 3 together, first, the WLANmodule 100 of the wireless device operates in a normal mode andestablishes a WiFi link to a communication device (step S210). In stepS220, the WLAN module 100 continues to monitor/detect a data rate ofdata packets transmitted to the communication device and obtains a PERcorresponding to the ACK messages from the communication device inresponse to the transmitted data packets. In the WLAN module 100, theprocessor 160 obtains the data rate of data packets transmitted to thecommunication device according to the modulation operations of the TX/RXprocessing unit 150. Once it is detected that the PER is good (i.e. thePER does not exceed a threshold PER_(th)) and the data rate reaches ahighest data rate that can be supported by the WLAN module 100 (stepS230), such as 11 Mbps for the 802.11b specification, 54 Mbps for the802.11g specification or MCS7 for the 802.11n specification, the WLANmodule 100 enters a power conservation mode (step S240), and then theprocessor 160 provides the control signal Ctrl to the PA 140, todecrease transmission power. Next, the WLAN module 100 checks whetherthe PER is still good (i.e. the PER does not exceed the thresholdPER_(th)) (step S250). If no (i.e. the PER exceeds the thresholdPER_(th)), the WLAN module 100 returns back to the normal mode, and theprocessor 160 provides the control signal Ctrl to the PA 140, to recoverthe transmission power (i.e. increase transmission power) (step S270),and then step S220 is performed to continue monitoring the data rate andthe PER. On the contrary, if the PER is good (i.e. the PER does notexceed the threshold PER_(th)), the WLAN module 100 continues to operatein the power conservation mode, so as to transmit the data packets withlower transmission power to the communication device (step S260). Thus,power consumption of the WLAN module 100 is decreased. In addition, theWLAN module 100 periodically checks the PER in the power conservationmode (step S250), so as to determine whether to return to the normalmode. In the power conservation mode, the wireless device of theinvention may decrease the current transmission power according apredefined scale, such as 1 dB, 3 dB (i.e. a half of the currenttransmission power) and so on, so as to obtain an optimal transmissionpower without affecting the PER. Furthermore, the wireless deviceperforms the method of FIG. 3 without additional circuits and complexoperations due to the data rate and the PER being given. In other words,it is easy to implement the method for controlling transmission power ofa wireless device according to the embodiment. In the embodiment, thethreshold PER_(th) is determined according to actual applications.

TABLE 1 shows an example illustrating the relationships between the datarate, transmission power and power consumption of various WiFi modesaccording to the method of FIG. 3. Taking the 802.11b specification asan example, when a wireless device uses a highest data rate 11 Mbps totransmit data packets to a communication device in a normal mode andobtains a good PER in response to the transmitted data packets, thewireless device will enter a power conservation mode, to decrease thetransmission power from 18 dBm to 13 dBm. Thus, power consumption of thewireless device is decreased from 260 mA to 170 mA.

TABLE 1 Transmission power Power consumption Mode Data rate (dBm) (mA)802.11b  1 Mbps 18 260 (Normal mode)  2 Mbps 18 260 (Normal mode) 5.5Mbps  18 260 (Normal mode) 11 Mbps 18 260 (Normal mode) 11 Mbps 13 170(power conservation mode) 802.11g  6 Mbps 13 170 (Normal mode)  9 Mbps13 170 (Normal mode) 12 Mbps 13 170 (Normal mode) 18 Mbps 13 170 (Normalmode) 24 Mbps 13 170 (Normal mode) 36 Mbps 13 160 (Normal mode) 48 Mbps13 140 (Normal mode) 54 Mbps 13 140 (Normal mode) 54 Mbps 10 100 (powerconservation mode) 802.11n MCS0 13 170 (Normal mode) MCS1 13 170 (Normalmode) MCS2 13 170 (Normal mode) MCS4 13 170 (Normal mode) MCS5 13 160(Normal mode) MCS6 13 140 (Normal mode) MCS7 13 140 (Normal mode) MCS710 100 (power conservation mode)

Referring back to FIG. 2, the RF module 120 may further use a measurecircuit to obtain a received signal strength indicator (RSSI) accordingto the RF signal RF_(in) that comprises the ACK messages from thecommunication device in response to the data packets transmitted by thewireless device, and provide the RSSI to the processor 160 of theBaseband chip 110. The measure circuit may be an independent circuit ormay be integrated into the LNA 130 or the TX/RX processing unit 150.FIG. 4 shows a method for controlling transmission power of a wirelessdevice with the WLAN module 100 of FIG. 2 according to anotherembodiment of the invention. Referring to FIG. 2 and FIG. 4 together,first, the WLAN module 100 of the wireless device operates in a normalmode and establishes a WiFi link to a communication device (step S310).In step S320, the WLAN module 100 continues to monitor/detect a datarate of data packets transmitted to the communication device and obtainsan RSSI corresponding to the ACK messages from the communication devicein response to the transmitted data packets. Once it is detected thatthe RSSI is good (i.e. the RSSI exceeds a threshold RSSI_(th)) and thedata rate reaches a highest data rate that can be supported by the WLANmodule 100 (step S330), such as 11 Mbps for the 802.11b specification,54 Mbps for the 802.11g specification or MCS7 for the 802.11nspecification, the WLAN module 100 enters a power conservation mode(step S340), and then the processor 160 provides the control signal Ctrlto the PA 140, to decrease transmission power. Next, the WLAN module 100checks whether the PER is good (step S350). If no (i.e. the PER exceedsthe threshold PER_(th)), the WLAN module 100 returns back to the normalmode, and the processor 160 provides the control signal Ctrl to the PA140, to recover the transmission power (i.e. increase transmissionpower) (step S370), and then step S320 is performed to continuemonitoring the data rate and the RSSI. On the contrary, if the PER isgood (i.e. the PER does not exceed the threshold PER_(th), the WLANmodule continues to operate in the power conservation mode, so as totransmit the data packets with lower transmission power to thecommunication device (step S360). Thus, power consumption of the WLANmodule 100 is decreased. In addition, the WLAN module 100 periodicallychecks the PER in the power conservation mode (step S350), so as todetermine whether to return to the normal mode. In the embodiment, thethreshold PER_(th) and RSSI_(th) are determined according to actualapplications.

FIG. 5 shows an exemplary diagram illustrating the relationships betweena data rate and input power (RSSI). In FIG. 5, the wireless device willswitch to a power conservation mode from a normal mode when the datarate reaches a highest value such as 54 Mbps and the input power issustained at a good quality such as a value larger than −60 dBm, thusthe transmission power drops to 10 dBm from 13 dBm.

FIG. 6 shows a method for controlling transmission power of a wirelessdevice with the WLAN module 100 of FIG. 2 according to anotherembodiment of the invention. Referring to FIG. 2 and FIG. 6 together,first, the WLAN module 100 of the wireless device operates in a normalmode and establishes a WiFi link to a communication device (step S602).In step S604, the WLAN module 100 continues to monitor a data rate ofdata packets transmitted to the communication device and obtains a PERin response to the transmitted data packets. Next, it is determinedwhether the PER is good (step S606). If no (i.e. the PER exceeds thethreshold PER_(th)), the WLAN module 100 decreases the data rate of datapackets (step S610). Otherwise, if the PER has not exceeded thethreshold PER_(th)), the WLAN module 100 continues to monitor the datarate (step S608), to detect whether the data rate has reached a highestdata rate that can be supported by the WLAN module 100 (step S612), suchas 11 Mbps for the 802.11b specification, 54 Mbps for the 802.11gspecification or MCS7 for the 802.11n specification. If the data ratehas not reached the highest data rate, the WLAN module 100 increases thedata rate of data packets (step S614), and then step S606 is performedto continue monitoring the PER. Otherwise, the WLAN module 100 enters apower conservation mode (step S616), and then the processor 160 providesthe control signal Ctrl to the PA 140, to decrease transmission power.Next, the WLAN module 100 checks whether the PER is still good (stepS618). If no (i.e. the PER exceeds the threshold PER_(th)), the WLANmodule 100 returns back to the normal mode, and the processor 160provides the control signal Ctrl to the PA 140, to recover thetransmission power (i.e. increase transmission power) (step S620), andthen step S604 is performed to continue monitoring the data rate. On thecontrary, if the PER is good (i.e. the PER does not exceed the thresholdPER_(th)), the WLAN module 100 continues to operate in the powerconservation mode, so as to transmit the data packets with the decreasedtransmission power (step S622). Thus, power consumption of the WLANmodule 100 is decreased. In addition, the WLAN module 100 periodicallychecks the PER in the power conservation mode (step S618), so as todetermine whether to return to the normal mode. In the embodiment, thethreshold PER_(th) is determined according to actual applications.

FIGS. 7A and 7B show a method for controlling transmission power of awireless device with the WLAN module 100 of FIG. 2 according to anotherembodiment of the invention. Referring to FIG. 2 and FIGS. 7A and 7Btogether, first, the WLAN module 100 of the wireless device operates ina normal mode and establishes a WiFi link to a communication device(step S702). In step S704, the WLAN module 100 continues to monitor adata rate of data packets transmitted to the communication device andobtains a PER in response to the transmitted data packets. Next, it isdetermined whether the PER is good (step S706). If no (i.e. the PERexceeds a threshold PER_(th)), the WLAN module 100 decreases the datarate of data packets (step S710). Otherwise, if the PER has not exceededthe threshold PER_(th), the WLAN module 100 continues to monitor thedata rate (step S708), to detect whether the data rate has reached ahighest data rate that can be supported by the WLAN module 100 (stepS712), such as 11 Mbps for the 802.11b specification, 54 Mbps for the802.11g specification or MCS7 for the 802.11n specification. If the datarate has not reached the highest data rate, the WLAN module 100increases the data rate of data packets (step S714), and then step S706is performed to continue monitoring the PER. Otherwise, the WLAN module100 further monitors an RSSI (step S716). Next, it is determined whetherthe RSSI exceeds a predetermined threshold RSSI_(th) (step S718). If theRSSI has not exceeded the predetermined threshold RSSI_(th), step S704is performed to continue monitoring the data rate. Otherwise, the WLANmodule 100 enters a power conservation mode (step S720), and then theprocessor 160 provides the control signal Ctrl to the PA 140, todecrease transmission power. Next, the WLAN module 100 checks whetherthe PER is good (step S722). If no (i.e. the PER exceeds the thresholdPER_(th)), the WLAN module 100 returns back to the normal mode and theprocessor 160 provides the control signal Ctrl to the PA 140 to recoverthe transmission power (step S724), and then step S704 is performed tocontinue monitoring the data rate. On the contrary, if the PER is good(i.e. the PER does not exceed the threshold PER_(th)), the WLAN module100 continues to operate in the power conservation mode to transmit thedata packets with the decreased transmission power (step S726), thuspower consumption of the WLAN module 100 is decreased. In addition, theWLAN module 100 periodically checks the PER in the power conservationmode (step S722), so as to determine whether to switch back to thenormal mode. In the embodiment, the threshold PER_(th) and RSSI_(th) aredetermined according to actual applications.

FIG. 8 shows a schematic diagram illustrating a mobile networkcommunication system according to an embodiment of the invention. InFIG. 8, all electrical devices 10, 20, 30, 40 and 50 are equipped withWLAN modules (e.g. 802.11b, 802.11g or 802.11n specifications) toperform data communications, wherein the device 10 camps on a cellularstation 60 of a service network. The wireless communications between thedevice 10 and the service network may be in compliance with variouswireless technologies, such as the Global System for Mobilecommunications (GSM) technology, General Packet Radio Service (GPRS)technology, Enhanced Data rates for Global Evolution (EDGE) technology,Wideband Code Division Multiple Access (WCDMA) technology, Code DivisionMultiple Access 2000 (CDMA 2000) technology, Time Division-SynchronousCode Division Multiple Access (TD-SCDMA) technology, WorldwideInteroperability for Microwave Access (WiMAX) technology, Long TermEvolution (LTE) technology, LTE Advanced (LTE-A) technology, and others.In FIG. 8, the device 10 functions as a hotspot in WiFi technology,which offers Internet access for the devices 20, 30, 40 and 50, thus thedevices 20, 30, 40 and 50 can access an Internet network through thedevice 10 and the cellular station 60 of the service network. In FIG. 8,the device 10 may use different or the same data rates to transmitpackets to the devices 20, 30, 40 and 50. Therefore, when the device 10transmits packets to at least one of the devices 20, 30, 40 and 50 witha highest data rate (e.g. 11 Mbps for the 802.11b specification, 54 Mbpsfor the 802.11g specification or MCS7 for the 802.11n specification) andobtains a good PER (or RSSI) corresponding to the highest data rate, thedevice 10 may determine whether to decrease transmission power accordingthe data rates of the devices other than the one with the highest datarate and the corresponding PERs or RSSIs. Specifically, according to thedata rates of the packets transmitted to various devices 20, 30, 40 and50 and the corresponding PERs or RSSIs, the device 10 will appropriatelycontrol its transmission power according to the methods of the inventionwithout affecting packet transmissions, so as to decrease powerconsumption of the wireless device 10.

FIG. 9 shows a schematic diagram illustrating an internet networkcommunication system according to an embodiment of the invention. InFIG. 9, the electrical device 80 transmits data packets to an Internetnetwork 90 through a wireless access point (AP) device 70. As describedabove, when the electrical device 80 transmits data packets with ahighest data rate (e.g. 11 Mbps for the 802.11b specification, 54 Mbpsfor the 802.11g specification or MCS7 for the 802.11n specification),the electrical device 80 may further determine whether to enter a powerconservation mode according to the corresponding PER or RSSI.Specifically, if the electrical device 80 obtains a good PER (or RSSI)corresponding to the highest data rate, the wireless device 80 willappropriately control its transmission power without affecting packettransmissions, so as to decrease power consumption.

The embodiments of the innovation disclose the methods to controltransmission power (i.e. output power) of a wireless device which usesIEEE 802.11 WiFi communication technologies to transmit data packets toother wireless devices. When the wireless device uses a highest datarate to transmit the data packets to the other wireless devices, thewireless device will enter a power conservation mode to decrease itstransmission power without degrading communication quality. Therefore,power consumption is decreased for the wireless device; especially, forshort-distances in a peer to peer mode or access mode.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

What is claimed is:
 1. A method for controlling transmission power of awireless device, comprising: establishing a WiFi link to a communicationdevice; transmitting data packets to the communication device accordingto a first transmission power; adjusting a data rate of the data packetsaccording to a packet error rate (PER); transmitting data packets to thecommunication device according to a second transmission power smallerthan the first transmission power when the data rate of the data packetsreaches a highest data rate and the PER satisfies a specific condition;and transmitting data packets to the communication device according tothe first transmission power when the data rate of the data packetsreaches the highest data rate and the PER does not satisfy the specificcondition; obtaining a received signal strength indicator (RSSI)corresponding to the communication device; and wherein the step oftransmitting data packets to the communication device according to thesecond transmission power further comprises: transmitting data packetsto the communication device according to the first transmission powerwhen the data rate of the data packets reaches the highest data rate,the PER does not exceed a first predetermined threshold and the RSSIdoes not exceed a second predetermined threshold; and transmitting datapackets to the communication device according to the second transmissionpower when the data rate of the data packets reaches the highest datarate, the PER does not exceed a first predetermined threshold and theRSSI exceeds the second predetermined threshold.
 2. The method asclaimed in claim 1, wherein the step of adjusting the data rate of thedata packets according to the PER further comprises: decreasing the datarate of the data packets when the PER exceeds a predetermined threshold;and increasing the data rate of the data packets when the PER does notexceed the predetermined threshold and the data rate does not reach thehighest data rate.